The prior art is documented with examples of swing training devices, a first example of this being shown in US 2007/0232404 to Begert which teaches a multi-sport training apparatus for teaching and improving hitting and throwing skills. Features include an adjustable waist belt with a buckle and a resilient connector having a distal end and a proximal end. Two clamps are disposed on the waist belt such that when the waist belt is worn at least one clamp is located near the iliac crest of the user's leading hip and may be employed for adjustably capturing and retaining the proximal end of the resilient connector. A swivelable clip is disposed on the distal end of said resilient connector, a sports implement/hand connector having a hook for attachment to the clip.
U.S. Pat. No. 6,375,581, to Urban et al., teaches an instructional swing device for teaching the proper swing for baseball, golf or the like. The instructional swing device includes a vest or harness arrangement which positions an adjustable, stretchable strap across the torso of the user from one shoulder to the opposite hip. Attached to the strap is an audible indicating mechanism, such as a buzzer, which is activated by proper movement of the user through stretching of the strap. In operation, the audible indicating mechanism identifies a proper swing during use to provide feedback to the user that the user is performing the desired hip movement in advance of the hands.
U.S. Pat. No. 8,512,171, to Minotti, teaches a batter training apparatus and method for training batters to attain optimal biomechanics for most effectively hitting a ball, with a proper rotation of a batter's hips and proper follow through with a batter's arms, wrists and shoulders. The training apparatus includes a belt worn over the hips that has a cable extending behind and between the hips. A tether connects the belt to a support post, preventing forward motion of the batter's body, but allowing and conditioning the hips to rotate. The support post sits at the rear of a platform that is about the size of a batter's box. An elastic cord connected to a forward arm and attached to the front of the platform, pulls a batter's wrists, arms and shoulders forward during proper follow through, conditioning the batter to swing the bat efficiently.
Also of note is the relative hip motion athletic training device and method of Medin, III, U.S. Pat. No. 8,550,930, and which teaches a sport training device wearable by a human user, including an oblong resilient, flexible member diagonally connecting one side of a shoulder harness to the opposite side of a separate hip harness. The member is tensioned in the user's upright, untwisted standing position. During a swing or a baseball-type pitching action, as the user's hips properly rotate with respect to the user's shoulders, the tension reduces thus encouraging and indicating to the user the preferred relative hip rotation action. Adjustments are provided adjust the length and tension of the resilient member. A member which deflects uniformly under a compressive load can be used as a measuring device of the relative angle between the hip and shoulder.